1. Field of the Invention
This application relates to medical devices. Specifically, but not by way of limitation, this application relates to inserting medical devices into a patient where the trajectory of the medical device is adjustable from a remote location.
2. Background
When introducing a primary medical device to the inside of a patient, one type of procedure utilizes two additional devices that interact with the primary medical device to aid in precision introduction of the primary medical device. The primary medical device includes an active portion attached to a distal end that may include, but is not limited to: drug delivery capability; a tissue removal instrument such as a laser; an instrument for attaching an electrode; etc. An introducer is a secondary medical device that may be used in a surgical procedure to move a primary medical device along an introduction axis, into or out of the patient. The introducer may be attached to another secondary medical device called a trajectory guide that positions the introducer in the direction of the area to be explored in the patient.
It is important in precision surgical procedures such as neurosurgery that the exact position of the primary medical device is known in precise relation to the position of interest within the body of the patient. For this reason, the relative position of the primary medical device is carefully controlled by secondary medical devices such as introducers and trajectory guides. The trajectory guide fixes the introduction axis to be used by the introducer in three-dimensional space relative to the patient, and the introducer controls the position (depth inside the patient) of the primary medical device along the introduction axis.
To ensure that the secondary medical devices are accurately adjusted relative to the location of interest inside the patient, the trajectory guide must be fixed relative to a patient reference frame. The patient reference frame includes the actual patient, and other objects or devices that the patient is fixed in relation to. The trajectory guide may therefore be fixed directly to the patient in one embodiment. Alternatively, the trajectory guide may be fixed to an intermediate object such as a stereotactic headframe or similar object attached to an operating table, with the patient being fixed to the operating table. For real time imaging, various locating devices may then be attached to the patient reference frame and to the primary medical device reference frame to determine their locations with respect to each other. If retrospective images are being used instead of real time imaging, then the secondary medical devices may be aligned with respect to reference points called fiducials that are located on the patient and that are also visible on the retrospective images.
In real time imaging, the alignment procedure frequently involves the use of a magnetic resonance imaging (MRI) station such as a long bore MR scanner. The MR scanner allows the surgeon to locate the area of interest inside the patient, and to plot a trajectory towards the area of interest. Other types of tissue imaging such as CT and PET are also available.
FIG. 1 shows a ball and socket joint 114 that is used to adjust the manual trajectory guide 100. A base 110 is mounted to a patient using a number of screws 118. Once adjusted, an insertion guide 112 is locked in place with a lockring 116, thus fixing an insertion axis 113 in three dimensional space. When a trajectory guide or other secondary device is used in conjunction with a long bore MR scanner or similar tissue imaging device, adjusting the desired trajectory is frequently a lengthy, iterative process. This is because the surgeon cannot view the patient and adjust the secondary medical devices in “real time.” In real time imaging, the patient is inside the MR scanner, and the viewing station for the MR scanner is frequently located at a remote location from the patient. In order to view the MR image of the patient, the surgeon must be outside the long bore MR scanner, looking at the display screen. At the same time, in order to adjust the secondary medical devices, the surgeon must be near the patient, and not in a position to adequately view the display screen. The surgeon typically must remove the patient from the bore of the MR scanner, make an educated adjustment, then return the patient to the bore of the MR scanner, then return to the MR viewing screen to check on how successful the adjustment was. This process can take many iterations.
Although cables or hydraulics could be used to remotely control a secondary medical device, the distance of remote operation is limited. Connecting lines such as cables or hydraulic lines experience friction effects when the connecting lines become sufficiently long. Material compression/tension may also occur over long distances in the cables, housings, hydraulic fluid, etc. Forces such as friction and material compression/tension lead to less accurate adjustment of the secondary device. This effect increases as the remote distance between the patient and the surgeon increases.
Cable communication devices are typically also designed to be adjusted manually, which requires a human operator. In a situation where the surgeon viewing the MR image is several rooms away from the patient, or even miles away from the patient, a second local operator is required to adjust the secondary medical device. As discussed above, this operator must be relatively near the patient due to less accurate adjustments as the operator becomes more remote and the connecting lines become increasingly long.
Another approach that can be used in conjunction with an MR scanner uses a single unit actuator to control the primary medical device. A drawback with this device is that when used inside an MR scanner environment, the entire device must be manufactured to be MR compatible. Devices that are used inside the magnet of an MR imaging scanner cannot be manufactured using magnetic materials due to their interaction with the scanner magnet during operation. Certain non-magnetic metallic materials also interfere with the image being taken, and cannot be used. Even if used outside an MR scanner, the single unit nature of this approach requires the entire device to be sterilized between procedures, or disposed of after each use.
The present inventors have recognized a need for a trajectory guide that can be adjusted without removing the patient from an MR scanner between adjustments. What is also needed is a trajectory guide that can be operated in such a way as to eliminate the need for a second surgical operator in addition to the surgeon viewing the MR scanner image. What is also needed is a trajectory guide that minimizes the negative effects of friction and material compression associated with excessively long cable driven devices. What is also needed is and a trajectory guide that is manufactured to be disposable or convenient to sterilize between procedures.